The prior art has included a number of ultrasonic devices for abating, destroying or removing obstructive material within anatomical structures of the body, such as blood vessels. Examples of devices which purportedly utilize ultrasonic energy, alone or in conjunction with other treatment modalities, to remove obstructions from anatomical structures include those described in U.S. Pat. Nos. 3,433,226 (Boyd), 3,823,717 (Pohlman, et al.), 4,808,153 (Parisi), 4,936,281 (Stasz), 3,565,062 (Kuris), 4,924,863 (Sterzer), 4,870,953 (Don Michael, et al.), 4,920,954 (Aliiget, et al.), and 5,100,423 (Fearnot) as well as other patent publications W087-05739 (Cooper), W089-06515 (Bernstein, et al.), W090-0130 (Sonic Needle Corp.), EP316789 (Don Michael, et al.), DE3,821,836 (Schubert) and DE2,438,648 (Pohlman).
In particular, flexible ultrasound-delivering catheters have been utilized to recanalize blood vessels which have become obstructed by atherosclerotic plaque and/or thrombotic matter.
Previously filed U.S. patent application Ser. No. 07/640,190, entitled ULTRASONIC ANGIOPLASTY DEVICE INCORPORATING IMPROVED TRANSMISSION MEMBER AND ABLATION PROBE, of which this application is a continuation-in-part, describes percutaneously insertable ultrasound delivering catheters which are useable to ultrasonically ablate or remove obstructive matter from blood vessels. As disclosed in patent application Ser. No. 07/640,190, such ultrasound delivery catheters may be constructed of a flexible catheter sheath having an elongate ultrasound transmission member or wire extending longitudinally therethrough. The cross-sectional dimension of the ultrasound transmission member may be tapered or narrowed near the distal end of the member. While such tapering or narrowing of the cross-sectional diameter of the ultrasound transmission member will typically decrease its rigidity and improve its bendability at the region of the taper or narrowing, such tapering or narrowing of the ultrasound transmission member carries with it a resultant increase in amplitude of the ultrasonic energy being transmitted through such narrowed or tapered region. Such increase in amplitude at the narrowed or tapered region may give rise to an increased likelihood of breakage or fracture of the ultrasound transmission member.
To facilitate use of ultrasonic ablation techniques within small tortuous blood vessels or other anatomical structures, it is desirable to develop small-diameter ultrasound-delivery catheters which are sufficiently pliable and bendable, at least in their distal regions, to navigate tortuous anatomical configurations without undue likelihood of breakage or fracture of the ultrasound transmission member during use.
In view of the foregoing, there remains a need in the art for development of new ultrasound transmission members having improved pliability or bendability with minimal likelihood of breakage or fracture.